diff --git a/.changeset/field-group-targeted-selectors.md b/.changeset/field-group-targeted-selectors.md
new file mode 100644
index 00000000..73fccef9
--- /dev/null
+++ b/.changeset/field-group-targeted-selectors.md
@@ -0,0 +1,5 @@
+---
+"@styleframe/theme": patch
+---
+
+Fix field-group horizontal/vertical border joining to target known control classes (`.input`, `.textarea`, `.select`, `.button`, `.dropdown`) instead of all children (`*`), using `:where`/`:is` for correct specificity.
diff --git a/theme/src/recipes/field-group/useFieldGroupRecipe.test.ts b/theme/src/recipes/field-group/useFieldGroupRecipe.test.ts
index e88884d5..9c4d13c6 100644
--- a/theme/src/recipes/field-group/useFieldGroupRecipe.test.ts
+++ b/theme/src/recipes/field-group/useFieldGroupRecipe.test.ts
@@ -144,6 +144,9 @@ describe("useFieldGroupRecipe", () => {
 	});
 
 	describe("seam selectors", () => {
+		const C = `:where(.input, .textarea, .select, .button, .dropdown)`;
+		const K = `:is(.input, .textarea, .select, .button, .dropdown)`;
+
 		it("flattens horizontal seams and grows fields", () => {
 			const s = createInstance();
 			useFieldGroupRecipe(s);
@@ -152,10 +155,10 @@ describe("useFieldGroupRecipe", () => {
 			expect(horizontal).toBeDefined();
 
 			expect(
-				findChildRule(horizontal, "& > *:not(:last-child)")?.declarations,
+				findChildRule(horizontal, `& > ${C}:has(~ ${K})`)?.declarations,
 			).toMatchObject({ borderRightWidth: "0" });
 			expect(
-				findChildRule(horizontal, "& > *:not(:first-child)")?.declarations,
+				findChildRule(horizontal, `& > ${C} ~ ${K}`)?.declarations,
 			).toMatchObject({ borderTopLeftRadius: "0" });
 
 			for (const query of ["& > .input", "& > .select", "& > .textarea"]) {
@@ -174,10 +177,10 @@ describe("useFieldGroupRecipe", () => {
 			expect(vertical).toBeDefined();
 
 			expect(
-				findChildRule(vertical, "& > *:not(:last-child)")?.declarations,
+				findChildRule(vertical, `& > ${C}:has(~ ${K})`)?.declarations,
 			).toMatchObject({ borderBottomWidth: "0" });
 			expect(
-				findChildRule(vertical, "& > *:not(:first-child)")?.declarations,
+				findChildRule(vertical, `& > ${C} ~ ${K}`)?.declarations,
 			).toMatchObject({ borderTopLeftRadius: "0" });
 		});
 
diff --git a/theme/src/recipes/field-group/useFieldGroupRecipe.ts b/theme/src/recipes/field-group/useFieldGroupRecipe.ts
index 53a3f5af..3ffe7a0c 100644
--- a/theme/src/recipes/field-group/useFieldGroupRecipe.ts
+++ b/theme/src/recipes/field-group/useFieldGroupRecipe.ts
@@ -62,14 +62,26 @@ export const useFieldGroupRecipe = createUseRecipe(
 	(s) => {
 		const { selector } = s;
 
+		const fieldGroupChildren = [
+			".input",
+			".textarea",
+			".select",
+			".button",
+			".dropdown",
+		];
+		const C = `:where(${fieldGroupChildren.join(", ")})`; // subject anchor, 0 specificity
+		const K = `:is(${fieldGroupChildren.join(", ")})`; // adjacency key, (0,1,0) specificity
+
 		// Horizontal: join controls side-by-side and let fields take the slack.
 		selector(".field-group.-horizontal", {
-			"& > *:not(:last-child)": {
+			// non-last control (has a following control) → merge right edge into the next
+			[`& > ${C}:has(~ ${K})`]: {
 				borderTopRightRadius: "0",
 				borderBottomRightRadius: "0",
 				borderRightWidth: "0",
 			},
-			"& > *:not(:first-child)": {
+			// non-first control (preceded by a control) → square the left edge
+			[`& > ${C} ~ ${K}`]: {
 				borderTopLeftRadius: "0",
 				borderBottomLeftRadius: "0",
 			},
@@ -80,12 +92,12 @@ export const useFieldGroupRecipe = createUseRecipe(
 
 		// Vertical: join controls top-to-bottom.
 		selector(".field-group.-vertical", {
-			"& > *:not(:last-child)": {
+			[`& > ${C}:has(~ ${K})`]: {
 				borderBottomLeftRadius: "0",
 				borderBottomRightRadius: "0",
 				borderBottomWidth: "0",
 			},
-			"& > *:not(:first-child)": {
+			[`& > ${C} ~ ${K}`]: {
 				borderTopLeftRadius: "0",
 				borderTopRightRadius: "0",
 			},